Vehicles are increasingly implementing various efficiency systems for numerous purposes. Two popular efficiency systems relate to emissions control and fuel economy, for example. Devices associated with such efficiency systems are typically programmed to operate during predetermined operating conditions, such as during predetermined conditions of oil employed in conjunction with the engine.
Typically, oil viscosity is a property of the oil that determines appropriate usage of the efficiency system device. Oil temperature is often used to serve as an indicator of oil viscosity; however, the use of specific sensors to determine oil temperature is costly and therefore the oil temperature is often estimated in an effort to optimize use of the devices associated with the efficiency systems. Unfortunately, estimation of the oil temperature may be inaccurate, with the inaccuracies typically more prevalent during certain operating stages, such as a transient warm-up phase of the engine, for example. There are additional sources of inaccuracies associated with estimating oil viscosity, such as age of the oil, oil weight actually installed, oil brand and fuel dilution, and water contamination, for example.